Process of coating conducting materials with tin



' Patented Feb. 24, 19.25."

I v 1,527,576 1 UNITED STATES PATENT oFn-ca.

, ISAAC M. SCOTT AND SAMUEL PEAOOCK,

F WHEELING, WEST VIRGINIA,- AND WIL- LIAJYLEABL ARMSTRONG, OF MARTIN'SFERRY, OHIO, ASSIGNORS T0 WHEELING STEEL 8c IRON COMPANY, OF WHEELING,WEST VIRGINIA, A CORPORATION 0F c d WEST PROCESS OF coarme connuc'rraeMATERIALS 'wrrrr TIN,

No Drawing. Application filed February To all whomitmg/concem: v Be'itknown that we, ISAAC M. Soo'rr, SAMUEL PEACOCK, and'WIiJLIAM EARL ARM-'STRQNG, all citizens of the United States, the said ISAAC M. Scorr andSAMUEL PEA- COCK residing at Wheeling, in thecounty of Ohio and State ofWest Virginia, and the said WILLIAM EARL ARMSTRONG residing at MartinsFerry, in the county of Belmont and State of Ohio, have invented certainnew and useful Improvements in Processes of Coating Conducting Materialswith Tin, and we do hereby declare the following to be a full,clear,and=exact description of the invention, such as will enable'othersskilled a in the art to which it appertains to make v and use the same.V

's invention relates to improvements in electro-tinning and moreparticularly to the whereby said electroinning can be carried out on acommercial scale and in a manner more .economical'than has beenheretofore attained. y

With these andother objects in view the invention consists in the novelsteps and combinations of steps constituting the process, all as will bemore fully hereinafter dis-' closed and particularly pointed out in theac claims. a

' In order that. the preciseinvention may be the more clearly understoodit is said In the electro-deposition of tin, great'difliculty has beenheretofore experienced in producm'g' a dense and coherent deposit. Thisis especially. emphasized when the objects to ;be electro-tinned areconstructedof metals higher in the electro chemical series thanis tin,"such for example, as steel or iron. Heretofore, articles' constructedof metals, such as iron, were firstelectro'-plated with a metal lower inthe electrochemical series such for example as copper, and upon thislast named metal the 'But, solutions that areavailable for epositing thetin'directly on iron or steel deterioirate rapidly, and cannot 'be"operated son la ,commercial scale, economically, unless, as-

sociated with a suitable restoring solution;

These difficulties are all well known'in this 'art." A. On the otherhand, this inventiogi involves h electroa solution and a method "by :wh}

solution or electrol te, and to a process 'tm was de osited.

19, 192?. Serial'No. 620,009.

.tinning can be carried out without diflichlty and much moreefliciently' than heretofore;

and this solution can be used for plating directly on steel and othermetals higher in the electro chemical series. Further this method maybeused. for large scaleyopera tions with different concentrations andwithout causing a formation of. colloidal or spongy deposits as in theprior procedures.

he solutions contain a lower percentage of tin than those heretoforeemployed, they do not deteriorate o'r'hydrolize to an objectionableextent, and, they operate with almost 100% efliciency. This bat-h doesnot require a periodical addition of tin salts as heretofore, or inother words it is self. sustainm k It will be understood by thoseskilled in the art that the thickness 'of deposit .or amount .oftinplated' per unit of surface will depend upon the length of time andthe number of amperes used, irrespective of the .voltagefiaut of course,the lower the voltage 1 employed the more economical will be thedeposition. I w

It has been found in practice that with say to 1% volts, good depositsare obtamed with this solution. f r p In carrying out the invention inits preferred form, one may take, for example 3 parts by weight of acommercial hydrofluoric acid HF) and dissolve therein 1.6 parts by weigt of boric acid H BO These acids react with an evol form an acid knownas fluoboric acidior ution of heat and .borofluohydric acid, thesimplest formula r 1 of which is HBF In this acid, one dissolvesstannous oxide SnO until the acid has taken up the equivalent. of 1.35parts by Wei ht of metallic tin, leaving about 31% of t e acid presentin the free state.

By this means there is produced a solution of stannous fluoborateSn(BF.,) containing an excessof free fluoboric acid HBF 'Tojncrease theconductivity of this solution one adds a metallic saltof a metal higherin the electro-chemical, series than iron, and prefers for this purposethe addition of 1.3 arts by weight of aluminum sulphate A1 0 or 1.3 artsby weight of magnesium sulphate Mg0,. This solution is'then diluted withwater. to such a concentration that it will contain about 1% ounces ofmetallic tin to one gallon. In this diluted solution there is suspendedmetallic tin as an anode on a positive bus bar, and one suspends thearticles to be plated such as sheet steel, in the solution and connectsthem to the. negative bus bar whereby on the passage of a suitableelectric current, the steel articles become plated with metallic tin.

It has been found it is also desirable to add so-called addition agentsor brightening agents, such as molasses, gelatine, etc., to the solutionfor the purpose of obtaining somewhat improved and bright deposits. Itis preferred to use ordinary glue for this pur-' pose and in a quantityof about .03 ounce per gallon of solution, but a larger amount will notinterfere with the success of the process. I \p Instead of usingstannous oxide $110 for introducting the tin into this solution, one mayadd other tin salts, such as stannous hydrate Sn(OH) or may dissolve inthe solution metallic tin with or without the aid of the electriccurrent. It has been found that the economical addition of tin may alsobe obtained by suspending metallic tin as anodes in the solution,connected with a positive bus bar and-suspending metal strips,surrounded by porous cups in the solution,

7 the metal strips being connected to a negative bus bar. By the passageof a suitable electric current, such as that above disclosed, the tin isdissolved from the anodes into the solution and being unable to passinto the porous cups, it is taken up by the acid.

' When sufiicient tin has been dissolved the cups are removed and theplating continued.

In the foregoing. description there is disclosed a tin solution in asomewhat diluted form with an acid reaction, but the solution can beused in more concentrated forms such for example as in those having aplurality of times the concentration of that above mentioned. Thesolution can also be used in the neutral state and for certain purposesone prefers a neutral solution, for such last named solution isespecially desirable when chemically pure tin is being deposited.

The above solution has proved satisfactory for the deposition of tin onvarious metals such as iron, steel and copper. and therefore, it is notdesired to be limitedto the pro cedure set forth 'in thedescription.This

' solution and process may also be usedwith various modifications fornumerous purposes that will readily suggest themselves to those skilledin the art without departing from the spirit of my invention.

plating baths, a bath suitable for carrying out this process'isdisclosed and claimed What is claimed is 1. The process -of coating tinon electric conductors which consists in providing an electrolyticsolution containing tin dissolved in boro-fiuohydric acid; immersing thearticle to be coated in said solution; and passing "a current ofelectricity from said solution to said article to obtain the desired 0coating. v 2. The process of coating tin on an electric conductor whichconsists in. providing an electrolytic solution containing stannousfiuoborate and a salt ofa metal more electropositive than iron,immersing the article to be coated in said solution as a cathode; andpassing a current through said solution to said cathode to obtain thedesired coating.

3. The rocess of coating iron or steel with tin w ich consists inproviding a bath consisting essentially of stannous fluoborate;immersing the iron or steel article to be coated in said bath and makingthe same a cathode in an electrolyticcircuit; and passing a current toobtain the desired coating. 4;. The process of coating iron or steelwith tin which consists in providing a bath consisting essentially ofstannous fiuoborate admixed with free boro-fluohydric acid; immersingthe iron or steel article to be coated insaid bath and making the same acathode in an electrolytic circuit; and passing a current to obtain thedesired coating.

v5. The process of coating iron or steel with tin which consists inproviding abath .consisting essentially of stannous fluoborate oated insaid bath and making the same a c thode in an electrolytic circuit,- andpassi g a current to obtain the desired coating.

tures.

ISAAC M; SCOTT. f' SAMUEL PEACOCK.

In testimony whereof we'aflix our signa- WILLIAM EARL' ARMSTRONG. I

